This study contributes with real-life evidence of dose similarities between DET and GLAR in T2D patients in Denmark. No differences in daily doses of DET and GLAR were identified when administered once daily and when taking into account different factors that may influence insulin utilisation. Thus, use of DET and GLAR is not associated with different medical costs if the price and treatment algorithm are similar.
The results of this study are consistent with recent real-world studies from Europe and the US, which also did not find any significant dose differences between DET and GLAR in T2D patients [19–21].
The results of this study are also in line with available data from the Danish Medicines Agency on redeemed prescriptions to individuals in 2008 and 2009, which do not indicate differences in daily doses of DET and GLAR (unpublished observations).
The evidence from clinical trials comparing DET and GLAR is inconsistent in terms of dose-related findings. This study is consistent with the results of a clinical trial including 385 American T2D patients in a basal-bolus regimen, which did not find significant dose differences between DET and GLAR . On the other hand, our results conflict with the results of a clinical trial including 582 European T2D patients in a basal regimen  and a clinical trial including 319 European and American T2D patients in a basal-bolus regimen . Both studies found that the mean daily dose of DET was higher than the mean daily dose of GLAR. However, these differences were mainly due to differences in treatment algorithms with more DET patients on twice daily dosing compared to GLAR patients.
Clinical trials are often considered the gold standard, but they do not necessarily reflect clinical practice, and furthermore, clinical practice may differ between countries. Thus, real-world studies such as the present study play an important role in terms of providing evidence of actual insulin utilisation.
A major strength of this study is that data was collected directly from the treating physician giving precise information on prescribed insulin dose in units per day. The daily dose prescribed by the treating physician is not necessarily the same as the dose actually used by the patient. However, it does not seem likely that there are differences between DET and GLAR patients with regard to compliance, and therefore this should not influence the main conclusion of no significant dose differences between DET and GLAR. Overall, the risk of information bias is considered low in this study compared to other real-world studies where the daily insulin dose is calculated based on dispensing data [19–21].
Dose comparisons were strictly performed for the same treatment algorithm (once daily dosing of DET or GLAR) in accordance with the aim of the study (as it otherwise would include off-label use of GLAR). Patients with two or more daily injections − of which the majority was DET patients − were excluded in the analyses presented here which could be regarded as a limitation towards the ability to conclude on cost differences. However, multivariate regression analyses were performed with these patients included. The analyses confirmed the expected positive correlation between number of daily injections and daily insulin dose as well as dose similarities between DET and GLAR when administered twice daily (data not shown). The overall conclusion remained unchanged, i.e. no differences in daily doses of DET and GLAR were identified when taking into account different factors that may influence insulin utilisation, including treatment algorithm.
A limitation of this study is the sensitivity to selection bias as the participating GP offices and specialists were not selected randomly. However, the study population is large and diverse which makes it highly probable that the main conclusion of no significant dose differences between DET and GLAR in a once daily regime is representative for all T2D patients in Denmark.
Another limitation concerns the possibility of residual confounding. The existence of co-morbidities in T2D patients may influence insulin utilisation, but was not included in the multivariate regression models as data was not available. However, it is not likely that this would have changed the main conclusion of no significant dose differences between DET and GLAR as there are no compelling reasons to assume that co-morbidities differ between T2D patients treated with DET and GLAR.